I'm getting too high velocities in simple 2D geometry
 

I'm simulating co2 through a nozzle, using a 2d axysimmetric model like this:
http://i59.tinypic.com/2rdzwoj.png

The problem is that the velocity gives very high values in the inlet (around 1200m/s).

The inlet is pressure inlet, gauge pressure 14 bar and initial/supersonic 13.9bar. The model is transport of species co2+air, k-epsilon realizable.

Does anyone know what am i doing wrong or how to solve this?